Tony and I tried multiplayer in P3D 2.5 a while back and had the same jitter issue we used to have in FSX:SE before the FSX Thunderbirds guys told me about locking frame rates at 30 fps in FSX:SE. But that didn't work in P3D and they also said they hadn't sorted it out yet.

I just found this so it looks like it is possible. Just got to find out what we're missing... If anyone knows, please reply.

EDIT: I had volume down since my wife was asleep. With volume up they are talking about locking at 32 fps to get the smoothness!

There may also be some clues in one of the comments. Looking into it...